The present invention relates generally to polarization-insensitive optical circuits which have one or more polarization sensitive optical components.
Light is a vector field that has two primary and orthogonal polarization states or vector directions. Generally, the polarization states are referred to as the S and P polarizations in free space optics, or the TE (Transverse Electric) and TM (Transverse Magnetic) modes of optical waveguides. The performance of optical waveguides and optical devices is often sensitive to the polarization state. That is, the response of the device changes as the polarization state changes. This is particularly pronounced in integrated optical waveguides that are fabricated on dielectric substrates.
Many optical components are insensitive to the input state of polarization. In fiber optic telecommunications, the polarization state of an optical signal that has traveled down any length of fiber is unknown, random, and time varying (due to perturbations in the environment). However, many devices remain polarization sensitive to some degree, and this affects ultimate performance, yield, and cost. However, in many cases it is desirable to use polarization sensitive operators while maintaining an overall polarization independent optical circuit.
An apparatus and method for treating optical signals with polarization sensitive components while maintaining a polarization insensitive signal output, and which contain relatively non-complex structures and components are desirable.